The Influence of World-Sheet Boundaries on Critical Closed String Theory

TL;DR

This paper explores how boundaries in world-sheet string theory influence the behavior of closed strings, revealing effects like the stringy Higgs mechanism and constraints on spectra through boundary conditions.

Contribution

It introduces a BRST formalism analysis of open-closed string interactions with boundary conditions, highlighting new effects on the spectrum and mechanisms.

Findings

Neumann boundary conditions reproduce the stringy Higgs mechanism

Dirichlet conditions impose constraints on the closed-string spectrum

Open-string boundary states act as auxiliary or Lagrange multiplier fields

Abstract

This paper considers interactions between closed strings and open strings satisfying either Neumann or constant (point-like) Dirichlet boundary conditions in a BRST formalism in the critical dimension. With Neumann conditions this reproduces the well-known stringy version of the Higgs mechanism. With Dirichlet conditions the open-string states correspond to either auxiliary or Lagrange multiplier target-space fields and their coupling to the closed-string sector leads to constraints on the closed-string spectrum.